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Directorate-General for Health and Food Safety
Terms of reference
The Committee on the basis of the examination of the following "note for the file":
- Biodegradability of surfactants in detergents
And the following reports
- Possible problems for the aquatic environment related to surfactants in detergents
- New biodegradability test methods for surfactants in detergents
- Surfactant Ring Test-I
and other information available to it, is to conclude on the following questions in its Opinion:
1. Confirm whether the proposed biodegradability test does constitute an improvement from the environmental point of view in relation to the existing approach based on primary biodegradability, in the sense that all surfactants passing the "ready" test would pass as well the "primary" test.
2. Confirm whether the proposed tests ISO headspace, OECD B and OECD D are suitable for surfactants and that they can constitute a direct permission to marketing, on grounds related to biodegradability, in case of passing.
3. Advise on the circumstance, if any, under which the tests OECD A, OECD C, OECD E and OECD F might be allowed in this respect.
4. Advise on the desirability to allow preadaptation.
5. Advise on the desirability to keep the "10 days window".
6. Advise on the appropriate criteria and supplementary information needed for decisions or derogations for surfactants failing the ready test and passing the primary biodegradability.
Background
The Community has operated a policy of limited use of surfactants in detergents since the early 1970 s. The aim of the current legislation has been to solve the problem caused by surfactant foam in water systems. Certain pass-and-fail tests were developed which effectively banned chemicals likely to cause foaming.
The preceding detergent directives were based on primary biodegradability tests. Only some of the anionic and non-ionic surfactants could be tested according to the stipulated test methods.
Chemicals that pass these primary biodegradability tests do not possess surface active properties which means that these chemicals do not cause foam after proper treatment. However, it is estimated that 50% of the in use (including) soaps fall outside the scope of this legislation.
The existing legislation does not include methods to deal with cationic and amphoteric surfactants.
Definitions
According to the Annex 1 of Methods for the Determination of Ready Biodegradability (Annex V of Directive 92/32/EEC), the following definitions are proposed.
Primary Biodegradation: is the alteration in the chemical structure of a substance, brought about by biological action, resulting in the loss of specific properties of that substance.
Ultimate Biodegradation: is the level of degradation achieved when the test compound is totally utilised by micro-organisms resulting in the production of carbon dioxide (in aerobic conditions), water, mineral salts and new microbial cellular constituents (biomass).
Readily Biodegradable: is an arbitrary classification of chemicals which have passed certain specified screening tests for ultimate biodegradability; these tests are so stringent that it is assumed that such compounds will rapidly and completely biodegrade in aquatic environment under aerobic conditions.
Inherently biodegradable: is a classification of chemicals for which there is unequivocal evidence of biodegradation (primary or ultimate) in any recognised test of biodegradability.
Lag time: is the time from inoculation until the degradation percentage has increased to at least 10%.
Degradation time: is the time from the end of the lag time till the time that 90% of maximum level of degradation has been reached.
10-day window: is the 10-day period immediately following the attainment of 10% degradation.
Dissolved Organic Carbon (DOC): is the organic carbon present in solution or that which passes through a 0.45 m m filter or remains in the supernatant after centrifugation at 4000 g for 15 min.
General Comments
Detergents represent, in quantitative terms, the most relevant contaminants discharged in surface waters.
Even chemicals representing a relatively low share of the total, may be considered as high tonnage contaminants.
It has been estimated that roughly 97% of existing surfactants measured by tonnage would pass a screening for ready biodegradability. Thus, at present, surfactant chemicals which would fail the screening tests, are about 3% of the total annual production of surfactants. This means about 100000 tons per year, i.e. a relevant amount, particularly if we consider that they are almost completely discharged in surface water.
Moreover some surfactants and their degradation products have been recognised as endocrine active chemicals. Endocrine activity is now considered as one of the problems with higher priority in environmental pollution.
Finally, the technology and the market of surfactants is evolving (see, for example the increase in use of cationic surfactants in the last 20 years). Therefore, a detergent legislation should take into account not only the present situation but also possible future changes.
For all these reasons, detergents are a class of chemicals which need a very careful control. In particular, for most of these chemicals, ultimate degradation tests should be highly recommended. Moreover, the proposal of a voluntary agreement between the industry and the Commission and of a case by case evaluation (made in the conclusions of the "Study of possible problems for the aquatic environment related to surfactants in detergents") is unacceptable for such important chemicals, at least as far as notification and labelling are concerned. However, it can be of interest for risk assessment.
Answers to specific questions
Question 1
The OECD ready biodegradability tests (series 301 A to F) and the ISO Headspace CO2 Standard (14593) rely on ultimate biodegradability and are at the same level of stringency. These methods have been designed to select chemicals, which are rapidly degradable in aerobic compartments including activated sludge of communal wastewater treatment. The concept of ready biodegradability is also stringent when reaction products of the biodegradation process are concerned, whereas in the existing approach a surfactant that is rapidly transformed into a persistent product is not recognised as a potential threat for the environment.
Therefore the proposed method is an improvement from the environmental point of view.
Question 2
The ISO Headspace CO2 Standard (14593) is the test of preference for surfactants and can constitute a direct permission to marketing, on grounds related to biodegradability, in case of passing. A modified form of this test was subjected to a ring test by eleven laboratories in 1998. In the report ("EU Surfactant Ring Test - I" WRc Ref: EU 4697, May 1999), the method is recommended for inclusion in the Directive.
The OECD 301B (Modified Sturm Test) and OECD 301D (Closed Bottle Test) are also suitable but have more limitations with respect to physico-chemical and toxicological properties of the tested compound.
Question 3
The OECD 301C (MITI I) and 301F (Manometric Respirometry) are based on monitoring the oxygen consumption with an automated manometric respirometer. These methods require a rather high concentration of test substance and are less suitable for surfactants, which are relatively toxic. Inhibitory effects in a biodegradability test may give a false indication of non-biodegradation.
In the OECD 301A (DOC Die-Away Test) and 301E (Modified OECD Screening Test), the course of the biodegradation is monitored with dissolved organic carbon (DOC) analysis, which fails if the tested substance has a too low water solubility. Moreover in 301E the inoculum/compound ratio is unfavourable in view of inhibitory effects of surfactants.
Question 4
Pre-adaptation aims at improving the capacity of microorganisms to degrade a given product. This treatment is intended to provide the micro-organisms with enough time and information to adequately develop (to induce and synthesise) the molecular equipment that is required for enzymatic catabolism of the product. This is especially true in the case of products that: a) are seldom present in the current environment, b) need metabolic equipment with high specificity. These two conditions are usually not met by detergents.
Most of the interest of this treatment is rather in the "research" field where the search for molecular mechanisms is the goal.
The report of the inter-laboratory test, indicates that the mild pre-adaptation procedure did not produce significant effects on the biodegradation percentages. As usual in screening tests, the inoculum applied by the participants was derived from communal wastewater treatment plants. The microbial communities in such systems, activated sludge or secondary effluent, are already adapted to a wide variety of surfactants (either adaptation to toxicity or enzyme induction). Apparently, the mild pre-adaptation during seven days, according to the SCAS procedure and aiming at an increased metabolic activity and a decreased variability in test results, does not improve the performance of the inoculum.
Adopting the pre-adaptation step from a biodegradability test system has also the disadvantage of creating a controversy at the screening level. Generally in screening biodegradability tests, the use of unadapted or non-pre-exposed inoculum is mandatory to meet the criteria of "ready biodegradability" according to the OECD.
For the above mentioned reasons, the advice of the CSTEE is that, as a general rule, pre-adaptation is not deemed desirable in a first step of "routine evaluation" for notification of surfactants in detergents.
Question 5
In the concept of ready biodegradability, both in OECD Guidelines and in EU methods, the 10 days window is applied. In principle, the 10 days window criterion is introduced in order to make the test more stringent. This principle is usually successfully applied to standard testing on individual substances.
Nevertheless, in the particular case of surfactants, the 10 days window criterion is not a requirement for the desired stringency. There are many conceptual and technical reasons to support this statement.
- Surfactant degradation is generally characterised by a multiphase kinetics that may be inevitable with a mixed microflora and possibly a multi-component substrate.
- Some surfactants yield, during their degradation, intermediate metabolites which may have catabolic kinetics (rates) different from the parent product.
- Some metabolites interfere with the degradation process by inhibiting transformation of the parent molecule.
This constraining clause must not interfere with the aim of the ultimate biodegradability test, which is to assess the capability (of a percentage) of a product to be fully degraded in simple compounds during a 28-day period.
Therefore, the CSTEE deems it not necessary to keep the "10 days window" for assessing ready ultimate biodegradability of surfactants in detergents.
Question 6
For those surfactants, which pass the primary biodegradability but fail the ready test, the main concern regards the biological activity of the metabolites. In this respect, the CSTEE advice is that information on the toxicity of these metabolites is needed, together with their bioconcentration potential, as well as their partition to the sediment phase.
If recalcitrant metabolites are produced, they are likely to be high volume chemicals. Therefore a complete risk assessment should be performed, according to the relevant EU legislation on dangerous substances and to related Technical Guidance Documents. Moreover, if some metabolites are suspected for endocrine disrupting activity, it is recommended to have data on this particular hazard, as soon as validated protocols to assess this kind of effect will be available.
Conclusions
The advice of the CSTEE on the questions posed in the terms of reference is:
1. The proposed method is an improvement from the environmental point of view in relation to the existing approach based on primary biodegradability.
2. The methods ISO headspace, OECD B and OECD D are suitable for surfactants and can constitute a direct permission to marketing in case of passing. Nevertheless, the two OECD methods have some limitations of applicability with respect to properties of compounds to be tested.
3. The tests OECD A, OECD C, OECD E and OECD F are less suitable for surfactants.
4. Pre-adaptation is not deemed desirable for notification of surfactants in detergents.
5. To keep the 10 days window is not deemed necessary for assessing ready ultimate biodegradability of surfactants in detergents.
6. If a surfactant fails the ultimate but passes the primary screening test, a risk assessment with special emphasis on possible metabolites is needed for decisions on derogation for surfactants.
The Committee on the basis of the examination of the following "note for the file":
- Biodegradability of surfactants in detergents
And the following reports
- Possible problems for the aquatic environment related to surfactants in detergents
- New biodegradability test methods for surfactants in detergents
- Surfactant Ring Test-I
and other information available to it, is to conclude on the following questions in its Opinion:
1. Confirm whether the proposed biodegradability test does constitute an improvement from the environmental point of view in relation to the existing approach based on primary biodegradability, in the sense that all surfactants passing the "ready" test would pass as well the "primary" test.
2. Confirm whether the proposed tests ISO headspace, OECD B and OECD D are suitable for surfactants and that they can constitute a direct permission to marketing, on grounds related to biodegradability, in case of passing.
3. Advise on the circumstance, if any, under which the tests OECD A, OECD C, OECD E and OECD F might be allowed in this respect.
4. Advise on the desirability to allow preadaptation.
5. Advise on the desirability to keep the "10 days window".
6. Advise on the appropriate criteria and supplementary information needed for decisions or derogations for surfactants failing the ready test and passing the primary biodegradability.
Background
The Community has operated a policy of limited use of surfactants in detergents since the early 1970 s. The aim of the current legislation has been to solve the problem caused by surfactant foam in water systems. Certain pass-and-fail tests were developed which effectively banned chemicals likely to cause foaming.
The preceding detergent directives were based on primary biodegradability tests. Only some of the anionic and non-ionic surfactants could be tested according to the stipulated test methods.
Chemicals that pass these primary biodegradability tests do not possess surface active properties which means that these chemicals do not cause foam after proper treatment. However, it is estimated that 50% of the in use (including) soaps fall outside the scope of this legislation.
The existing legislation does not include methods to deal with cationic and amphoteric surfactants.
Definitions
According to the Annex 1 of Methods for the Determination of Ready Biodegradability (Annex V of Directive 92/32/EEC), the following definitions are proposed.
Primary Biodegradation: is the alteration in the chemical structure of a substance, brought about by biological action, resulting in the loss of specific properties of that substance.
Ultimate Biodegradation: is the level of degradation achieved when the test compound is totally utilised by micro-organisms resulting in the production of carbon dioxide (in aerobic conditions), water, mineral salts and new microbial cellular constituents (biomass).
Readily Biodegradable: is an arbitrary classification of chemicals which have passed certain specified screening tests for ultimate biodegradability; these tests are so stringent that it is assumed that such compounds will rapidly and completely biodegrade in aquatic environment under aerobic conditions.
Inherently biodegradable: is a classification of chemicals for which there is unequivocal evidence of biodegradation (primary or ultimate) in any recognised test of biodegradability.
Lag time: is the time from inoculation until the degradation percentage has increased to at least 10%.
Degradation time: is the time from the end of the lag time till the time that 90% of maximum level of degradation has been reached.
10-day window: is the 10-day period immediately following the attainment of 10% degradation.
Dissolved Organic Carbon (DOC): is the organic carbon present in solution or that which passes through a 0.45 m m filter or remains in the supernatant after centrifugation at 4000 g for 15 min.
General Comments
Detergents represent, in quantitative terms, the most relevant contaminants discharged in surface waters.
Even chemicals representing a relatively low share of the total, may be considered as high tonnage contaminants.
It has been estimated that roughly 97% of existing surfactants measured by tonnage would pass a screening for ready biodegradability. Thus, at present, surfactant chemicals which would fail the screening tests, are about 3% of the total annual production of surfactants. This means about 100000 tons per year, i.e. a relevant amount, particularly if we consider that they are almost completely discharged in surface water.
Moreover some surfactants and their degradation products have been recognised as endocrine active chemicals. Endocrine activity is now considered as one of the problems with higher priority in environmental pollution.
Finally, the technology and the market of surfactants is evolving (see, for example the increase in use of cationic surfactants in the last 20 years). Therefore, a detergent legislation should take into account not only the present situation but also possible future changes.
For all these reasons, detergents are a class of chemicals which need a very careful control. In particular, for most of these chemicals, ultimate degradation tests should be highly recommended. Moreover, the proposal of a voluntary agreement between the industry and the Commission and of a case by case evaluation (made in the conclusions of the "Study of possible problems for the aquatic environment related to surfactants in detergents") is unacceptable for such important chemicals, at least as far as notification and labelling are concerned. However, it can be of interest for risk assessment.
Answers to specific questions
Question 1
The OECD ready biodegradability tests (series 301 A to F) and the ISO Headspace CO2 Standard (14593) rely on ultimate biodegradability and are at the same level of stringency. These methods have been designed to select chemicals, which are rapidly degradable in aerobic compartments including activated sludge of communal wastewater treatment. The concept of ready biodegradability is also stringent when reaction products of the biodegradation process are concerned, whereas in the existing approach a surfactant that is rapidly transformed into a persistent product is not recognised as a potential threat for the environment.
Therefore the proposed method is an improvement from the environmental point of view.
Question 2
The ISO Headspace CO2 Standard (14593) is the test of preference for surfactants and can constitute a direct permission to marketing, on grounds related to biodegradability, in case of passing. A modified form of this test was subjected to a ring test by eleven laboratories in 1998. In the report ("EU Surfactant Ring Test - I" WRc Ref: EU 4697, May 1999), the method is recommended for inclusion in the Directive.
The OECD 301B (Modified Sturm Test) and OECD 301D (Closed Bottle Test) are also suitable but have more limitations with respect to physico-chemical and toxicological properties of the tested compound.
Question 3
The OECD 301C (MITI I) and 301F (Manometric Respirometry) are based on monitoring the oxygen consumption with an automated manometric respirometer. These methods require a rather high concentration of test substance and are less suitable for surfactants, which are relatively toxic. Inhibitory effects in a biodegradability test may give a false indication of non-biodegradation.
In the OECD 301A (DOC Die-Away Test) and 301E (Modified OECD Screening Test), the course of the biodegradation is monitored with dissolved organic carbon (DOC) analysis, which fails if the tested substance has a too low water solubility. Moreover in 301E the inoculum/compound ratio is unfavourable in view of inhibitory effects of surfactants.
Question 4
Pre-adaptation aims at improving the capacity of microorganisms to degrade a given product. This treatment is intended to provide the micro-organisms with enough time and information to adequately develop (to induce and synthesise) the molecular equipment that is required for enzymatic catabolism of the product. This is especially true in the case of products that: a) are seldom present in the current environment, b) need metabolic equipment with high specificity. These two conditions are usually not met by detergents.
Most of the interest of this treatment is rather in the "research" field where the search for molecular mechanisms is the goal.
The report of the inter-laboratory test, indicates that the mild pre-adaptation procedure did not produce significant effects on the biodegradation percentages. As usual in screening tests, the inoculum applied by the participants was derived from communal wastewater treatment plants. The microbial communities in such systems, activated sludge or secondary effluent, are already adapted to a wide variety of surfactants (either adaptation to toxicity or enzyme induction). Apparently, the mild pre-adaptation during seven days, according to the SCAS procedure and aiming at an increased metabolic activity and a decreased variability in test results, does not improve the performance of the inoculum.
Adopting the pre-adaptation step from a biodegradability test system has also the disadvantage of creating a controversy at the screening level. Generally in screening biodegradability tests, the use of unadapted or non-pre-exposed inoculum is mandatory to meet the criteria of "ready biodegradability" according to the OECD.
For the above mentioned reasons, the advice of the CSTEE is that, as a general rule, pre-adaptation is not deemed desirable in a first step of "routine evaluation" for notification of surfactants in detergents.
Question 5
In the concept of ready biodegradability, both in OECD Guidelines and in EU methods, the 10 days window is applied. In principle, the 10 days window criterion is introduced in order to make the test more stringent. This principle is usually successfully applied to standard testing on individual substances.
Nevertheless, in the particular case of surfactants, the 10 days window criterion is not a requirement for the desired stringency. There are many conceptual and technical reasons to support this statement.
- Surfactant degradation is generally characterised by a multiphase kinetics that may be inevitable with a mixed microflora and possibly a multi-component substrate.
- Some surfactants yield, during their degradation, intermediate metabolites which may have catabolic kinetics (rates) different from the parent product.
- Some metabolites interfere with the degradation process by inhibiting transformation of the parent molecule.
This constraining clause must not interfere with the aim of the ultimate biodegradability test, which is to assess the capability (of a percentage) of a product to be fully degraded in simple compounds during a 28-day period.
Therefore, the CSTEE deems it not necessary to keep the "10 days window" for assessing ready ultimate biodegradability of surfactants in detergents.
Question 6
For those surfactants, which pass the primary biodegradability but fail the ready test, the main concern regards the biological activity of the metabolites. In this respect, the CSTEE advice is that information on the toxicity of these metabolites is needed, together with their bioconcentration potential, as well as their partition to the sediment phase.
If recalcitrant metabolites are produced, they are likely to be high volume chemicals. Therefore a complete risk assessment should be performed, according to the relevant EU legislation on dangerous substances and to related Technical Guidance Documents. Moreover, if some metabolites are suspected for endocrine disrupting activity, it is recommended to have data on this particular hazard, as soon as validated protocols to assess this kind of effect will be available.
Conclusions
The advice of the CSTEE on the questions posed in the terms of reference is:
1. The proposed method is an improvement from the environmental point of view in relation to the existing approach based on primary biodegradability.
2. The methods ISO headspace, OECD B and OECD D are suitable for surfactants and can constitute a direct permission to marketing in case of passing. Nevertheless, the two OECD methods have some limitations of applicability with respect to properties of compounds to be tested.
3. The tests OECD A, OECD C, OECD E and OECD F are less suitable for surfactants.
4. Pre-adaptation is not deemed desirable for notification of surfactants in detergents.
5. To keep the 10 days window is not deemed necessary for assessing ready ultimate biodegradability of surfactants in detergents.
6. If a surfactant fails the ultimate but passes the primary screening test, a risk assessment with special emphasis on possible metabolites is needed for decisions on derogation for surfactants.
